Whiteboards are a great UML case tool. They help to make modelling a social activity. They help to emphasize that the act of modelling and the understanding it produces is just as valuable as the resulting model. The wipeability of whiteboards is also a great feature. It encourages modification and experimentation.
Whiteboards are not so good when you want to rearranging a diagram though. But... it occurred to me that if the whiteboard is magnetic then fridge-magnet-style UML-shapes might help. So I found a company that sells magnetic sheet and paid a bit extra to have it coated with a dry-wipe surface. The first sample arrived today and I've made my first prototypes. I cut out two sizes of rectangles and edged them with a permanent marker. Here's one of the larger ones (the background is a tablecloth not wallpaper!)
Now simply stick them on the whiteboard - they stick to each other of course:
Here's the big rectangles vertically in 3-section class format:
And horizontally for packages (just draw on the top-left tab):
Here's a 1-section only class diagram overview made from the smaller rectangles:
And just for Pete Goodliffe here's a Booch cloud:
I'm also going to cut out some ellipses for use-cases/scenarios and some rounded rectangles (roundtangles) for activities/states.